To determine which condition must be met in order for a chemical equation to be balanced, let's explore each of the given options:
1. The elements in the reactants are the same as the elements in the products.
- While it is true that the same elements appear on both sides of a balanced equation, this condition alone is not sufficient to ensure the equation is balanced. The quantities of these elements (in terms of atoms) must also match.
2. There are fewer elements in the reactants than there are in the products.
- This is incorrect. In a balanced equation, the quantity and types of elements must be consistent across both reactants and products.
3. The number of atoms in the reactants is greater than the number of atoms in the products.
- This statement is false. A balanced chemical equation cannot have a different number of atoms in the reactants compared to the products.
4. The number of atoms in the reactants equals the number of atoms in the products.
- This is the correct condition for a balanced equation. A balanced chemical equation must have the same number of each type of atom on both sides of the equation. This ensures that mass is conserved during the reaction.
Given these analyses, the condition that must be met in order for an equation to be balanced is that the number of atoms in the reactants equals the number of atoms in the products.
Hence, the correct answer is the fourth option:
- The number of atoms in the reactants equals the number of atoms in the products.
